The retention of arsenate by four soils of Saskatchewan, Canada, and its relation to selected soil properties and anionic environments were studied. The data indicate that As retention by the soils at the dilute, As concentration range studied does not proceed through the precipitation of sparingly soluble arsenate compounds. Arsenate retention evidently proceeds through adsorption mechanisms. The adsorption maxima of the soils are not related to acidity and the contents of inorganic C, but are linearly related to amounts of ammonium oxalate-extractable Al and, to a lesser extent, to the contents of clay and ammonium oxalate-extractable Fe. Chloride, nitrate, and sulfate present at concentrations usually present in saline soils have little effect on the adsorption of As. Phosphate substantially suppresses As adsorption by the soils, and the extent of the suppression varies from soil to soil.

Adsorption of arsenate by soils and its relation to selected chemical properties and anions.

A review on sources, identification and treatment strategies for the removal of toxic Arsenic from water system

New evidence shows that the number of hungry people in the world is growing, reaching more than 820 million in 2018 (one in every nine people), up from 812 million in 2017. There are three main causes of food insecurity: high exposure and vulnerability to climate extremes, conflicts, and economic slowdown. Paradoxically, every year, roughly one third of the food produced in the world for human consumption-approximately 1.3 billion tonnes-is lost or wasted. It is estimated that, if the food lost or wasted globally could be reduced by just one quarter, this would be sufficient to feed the people suffering from chronic hunger in the world. Rice, an important staple food for over half the world's population, is also affected. At the same time, evidence shows that the food lost or wasted is a major cause of greenhouse gas emission, which itself feeds into climate change and extreme weather, resulting in further food insecurity and malnutrition. This paper briefly introduces the Food and Agriculture Organization of the United Nations (FAO), presents the recent findings on the current situation of food security and nutrition in the world, and highlights the issue of food loss and waste and its impact on food security, with particular emphasis on the constraints it poses to the achievement of key Sustainable Development Goals (SDGs).

FAO and the Situation of Food Security and Nutrition in the World (Rice Science in Global Health : Proceedings of the 3rd International Symposium)

Antioxidants as modulators of arsenic-induced oxidative stress tolerance in plants: An overview

Antioxidants as modulators of arsenic-induced oxidative stress tolerance in plants: An overview.

The inessential heavy metal/loids cadmium (Cd) and arsenic (As), which often co-occur in polluted paddy soils, are toxic to rice. Silicon (Si) treatment is known to reduce Cd and As toxicity in rice plants. To better understand the shared mechanisms by which Si alleviates Cd and As stress, rice seedlings were hydroponically exposed to Cd or As, then treated with Si. The addition of Si significantly ameliorated the inhibitory effects of Cd and As on rice seedling growth. Si supplementation decreased Cd and As translocation from roots to shoots, and significantly reduced Cd- and As-induced reactive oxygen species generation in rice seedlings. Transcriptomics analyses were conducted to elucidate molecular mechanisms underlying the Si-mediated response to Cd or As stress in rice. The expression patterns of the differentially expressed genes in Cd- or As-stressed rice roots with and without Si application were compared. The transcriptomes of the Cd- and As-stressed rice roots were similarly and profoundly reshaped by Si application, suggesting that Si may play a fundamental, active role in plant defense against heavy metal/loid stresses by modulating whole genome expression. We also identified two novel genes, Os01g0524500 and Os06g0514800, encoding a myeloblastosis (MYB) transcription factor and a thionin, respectively, which may be candidate targets for Si to alleviate Cd and As stress in rice, as well as for the generation of Cd- and/or As-resistant plants. This study provides valuable resources for further clarification of the shared molecular mechanisms underlying the Si-mediated alleviation of Cd and As toxicity in rice.

Comparative physiological and transcriptomic analyses illuminate common mechanisms by which silicon alleviates cadmium and arsenic toxicity in rice seedlings.

Silicon (Si) has been shown to alleviate Cd stress in rice. Here, we investigated the beneficial effects of foliar Si in an indica rice Huanghuazhan (HHZ). Our results showed that foliar Si increases the dry weight and decreases Cd translocation in Cd-exposed rice at the grain-filling stage only, implying that the filling stage is critical for foliar Si to reduce Cd accumulation. We also investigated the transcriptomics in flag leaves (FLs), spikelets (SPs), and node Is (NIs) of Cd-exposed HHZ after foliar Si application at the filling stage. Importantly, the gene expression profiles associated with the Si-mediated alleviation of Cd stress were tissue specific, while shared pathways were mediated by Si in Cd-exposed rice tissues. Furthermore, after the Si treatment of Cd-exposed rice, the ATP-binding cassette (ABC)-transporters were mostly upregulated in FL and SP, while the bivalent cation transporters were mostly downregulated in FL and NI, possibly helping to reduce Cd accumulation. The genes associated with essential nutrient transporters, carbohydrate and secondary metabolite biosynthesis, and cytochrome oxidase activity were mostly upregulated in Cd-exposed FL and SP, which may help to alleviate oxidative stress and improve plant growth under Cd exposure. Interestingly, genes responsible for signal transduction were negatively regulated in FL, but positively regulated in SP, by foliar Si. Our results provide transcriptomic evidence that foliar Si plays an active role in alleviating the effects of Cd exposure in rice. In particular, foliar Si may alter the expression pattern of genes associated with transport, biosynthesis and metabolism, and oxidation reduction.

Comparative transcriptomics provide new insights into the mechanisms by which foliar silicon alleviates the effects of cadmium exposure in rice

In rice, moderate leaf rolling improves photosynthesis and crop yield. However, the molecular mechanisms underlying this important agronomic trait remain incompletely understood. Here, we investigated a dominant rolled leaf mutant (RL-D) developed from Nipponbare rice (WT). From the six-leaf stage, the leaves of the mutant rolled inward, and abnormal sclerenchyma tissues developed on the abaxial side of the leaf midribs. Additionally, leaf length, plant height, grain weight, and chlorophyll content were significantly greater in the mutant as compared to the WT. Genetic mapping analysis suggested that the leaf-rolling trait in the RL-D mutant was controlled by a single dominant gene, which was located in a 743-kb region on rice chromosome 3. Re-sequencing analysis showed that one gene in the mapped region encoding a protein phosphatase, Os03g0395100 (herein designated OsPP2C), had base mutations in the first exon. These mutations may have produced a truncated form of the OsPP2C protein in RL-D. Further transcriptomic analysis revealed that several biological processes, especially secondary cell wall formation and protein phosphorylation, were overrepresented among the differentially expressed genes (DEGs) between the mutant and the wild type. qRT-PCR verification also demonstrated that specific genes associated with leaf polarity and secondary cell wall formation were differentially expressed in the mutant. This study presents a novel dominant rolled-leaf germplasm that may help to improve rice leaf morphology in the future. The results also suggested that the RL-D phenotype might result from abnormal sclerenchyma tissue development, possibly regulated by OsPP2C via the dephosphorylation pathway. This may present a novel mechanism underlying leaf-rolling in rice.

Genetic Mapping and Transcriptomic Analysis Revealed the Molecular Mechanism Underlying Leaf-Rolling and a Candidate Protein Phosphatase Gene for the Rolled Leaf-Dominant (RL-D) Mutant in Rice

Huamei Chen

Papers

Comparative physiological and transcriptomic analyses illuminate common mechanisms by which silicon alleviates cadmium and arsenic toxicity in rice seedlings.

Comparative transcriptomics provide new insights into the mechanisms by which foliar silicon alleviates the effects of cadmium exposure in rice

Genetic Mapping and Transcriptomic Analysis Revealed the Molecular Mechanism Underlying Leaf-Rolling and a Candidate Protein Phosphatase Gene for the Rolled Leaf-Dominant (RL-D) Mutant in Rice